Turbochargers typically include a turbine section with a housing and a turbine wheel rotatably supported in a flow passage of the housing. The turbine wheel rotates as a fluid (e.g., exhaust gas) flows through the flow passage of the housing.
The performance of the turbine section may be expressed in terms of efficiency as a function of flow at a given expansion ratio. Typically, the turbine exhibits high efficiency at a particular volumetric flow rate, and as the flow deviates from this flow, the efficiency is negatively impacted. At the same time, the efficiency of turbines has a relationship with the amount of flow a turbine can pass for a specific external diameter and throat area (minimum geometric area in the passage between adjacent turbine blades) of the turbine wheel. Generally speaking, there is a nominal flow capacity beyond which the maximum efficiency is compromised. Together, this means that there is a maximum flow capacity a turbine can deliver at a given expansion ratio for a targeted efficiency level for a given turbine wheel size.
However, it may not be possible to increase the turbine wheel size to allow for a desired flow capacity for a given efficiency target. For example, increasing the turbine wheel size may cause the turbocharger to be too bulky for a particular vehicle.
Accordingly, it is desirable to provide a turbocharger with a relatively small turbine wheel that provides increased efficiency at a relatively high flow rate and that ultimately increases efficiency at that flow condition. Other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background discussion.